Map holder and plotting device



April 19, 1938. P. DALTON 2,114,652 MAP HOLDER AND PLOTTING DEVICE FiledNov. 1, 1935 3 Sheets-Sheet l April 19, 1938. DALTON MAP HOLDER ANDPLOTTING DEVICE Filed Nov. 1, 1935 3 Sheets-Sheet 2 Amifi 19, 19389 P.DALTON 2,114,652

' MAP HOLDER AND PLOTTING DEVICE Filed Nov. 1, 1935 3 Sheets-Sheet 3Patented Apr. 19, 1938 UNITED STATES PATENT OFFICE 2,114,s52 MAP HOLDERAND PLOTTING DEVICE. Philip Dalton, Washington, D. 0. ApplicationNovember 1,1935, Serial No. 47,882

1'7 Claims.

My invention relates to improvements in combined map holders andplotting devices.

It is desirable in'the navigation of aircraft to use a map on which toplot courses and distances,

radio compass bearings, astronomical lines of position, etc. The use ofan ordinary chart table on which to do this work, using the well knownprotractors, rulers, dividers, etc., is difficult and inconvenientexcept in the larger planes. As a matter of fact, in any plane it isoften advantageous and sometimes necessary for the pilot or co-pilot todo this work without leaving the controls. It is, therefore, an objectof my invention to provide a simple, compact, durable and inexpensivemap holder and plotting device which may be constructed without anyloose parts other than a pencil so that it can be effectively used inthe pilots lap while he is in the control seat of an aeroplane.

Another object of my invention is to provide such a map holder which canbe easily and quickly used to measure and plot directions and distancesover a map as well as to solve the vector triangles encountered inaerial dead reckoning navigation.

' A further object of my invention is to provide such a device withwhich it is easy to measure or plot directions over a map with referenceto both true north and magnetic north.

Another object of my invention is to provide a map holder and plottingdevice which is adapted to use a wide variety of maps of different sizesand shapes without cutting or mutilating them.

In its preferred form my invention includes a transparent plotting sheetwith a writing surface, and a second transparent sheet pivotally mountedbeneath it. The second transparent sheet has a grid and a counterclockwise compass rose printed thereon, the counter clock-wise compassrose being concentric with the pivotal point.

This assembly is in turn securely mounted over a base member adapted tohold a map.

It will be understood that my invention is not only useful for aerialnavigation but also for navigation in general, surveying, artilleryplotting and reconnaissance, in fact for any plotting problem whereinconsiderations of space, weight, ease of carrying, manipulation, etc.,make it impractical to use the ordinary chart holder or plane tabletogether with the usual accessories.

My invention will be better understood from the following descriptiontaken in connection with the accompanying drawings, and the features of55 novelty which characterize the same will; be

pointed outwith particularity in the claims annexed to and forming apart of this specification.

Referring to the drawings, Figure l is a plan view of my map holderplotting device partly broken away to show the different members. Fig- 5ure 2 is an expanded side elevation partly in section showing how thedevice is assembled. Figure 3 is a diagram illustrating the use of myinvention to solve well known problems in aerial navigation. Figure 4 isa diagrammatic side ele- 10 vation showing a modification arranged foruse at night. Figs. 5, 6, and 7 show the component parts of thepreferred form and two modifications respectively;

Referring to Figs. 1, 2 and 5, the preferred embodiment of my inventionconsists of a flat, square base piece I around which a standard scaleaviation map 2 is folded in such a manner that the two adjacent squareareas in which it is desired to navigate appear onopposite sides of 20the base piece I. The base piece I may be fash-- ioned of any suitablematerial, such for example as plywood. By folding the map around thisbase piece I it is possible to fold underneath, areas of a standardairway map which are not 25 being used without cutting or damaging themap. Secured on each side of the base piece I which has the map foldedtherearound, are square pieces of celluloid 3, hereafter referred to asplot,- ting sheets, substantially the same size as the 30 base piece I.These pieces of celluloid are so treated on their upper sides as topresent plotting surfaces upon which pencil marks may be easily made anderased. The plotting sheets 3 are secured to each other on oppositesides of the base' piece I by means of rubber bands 4- secured to hooks5 on each corner of each of the plotting sheets 3.

It will be understood, of course, that any suitable fastening means maybe used. With the arrangement shown the rubber band fastening meansaccomplishes the function of positioning each of the plotting sheets 3with respect to the base piece I and map 2 during use, as well as thefunction of holding the component parts together. Further. it enablesone to unfasten two corners of the plotting sheets and open them up toremove the base piece I and map 2, the two remaining rubber bandsforming a hinge during this operation. 7

A transparent grid disc or protractor sheet 6 is rotatably mountedbetween each of the plotting sheets 3 and the map 2. This rotatablemounting is achieved by means of pivot I securing the center points ofgrid discs 6. to the center points of plotting sheets 3. Each of thesegrid discs 6 is larger in diameter than its associated plotting sheet 3so that the edge thereof extends beyond plotting sheet 3. Thisarrangement makes it possible to easily manipulate grid discs 6 androtate them'to any position desired. Each of the grid discs 6 hasdelineated thereon a circle 8 concentric with the pivotal point. Thiscircle 8 is made on a radius of 100 miles to the scale of the map withwhich the device is to be used and is divided into a reversed orcounter-clockwise compass rose., A diametric line 9 extends through the-180 or north-south points of the compass rose with arrows pointing inthe direction of 0. This line 9 is divided into two radial scales ofmiles having their origins at the pivotal point. A series of lines 9' isdelineated over the entire surface of the grid disc 6, said lines beingparallel to diametric line 9 and spaced apart by a distance equivalentto ten miles based on the above referred to scale of miles. A secondseries of lines i0 is delineated on grid disc 6 at right angles todiametric line 9, said lines being likewise spaced every ten miles inaccordance with the scale of miles. These two series of lines 9' and I0respectively form a grid laid out in accordance with the scale of themap being used.

Index T pencil-marked on plotting sheet 3 indicates true north inaccordance with one of the meridians on map 2. Index M, likewisepencilmarked on plotting sheet 3, indicates magnetic north in accordancewith the indication on map 2 that the magnetic variation for the areashown is west.

Lines 9' used in conjunction with the compass rose 8 and pencil markedindices T and M provide a means for plotting freehand on one of theplotting sheets 3, the direction between any two points on map 2. At thesame time, lines I0 provide a means for measuring the distance betweesuch two points. 7

The manner of using my invention will be well understood to thosefamiliar with the art of aerial navigation from a consideration of Fig.3. This figure illustrates the method for solving the wind drift problemto make good a course CA, C and A being selected points on map 2.

The first step in the use of my invention after it has been assembledwith the proper map areas showing beneath the plotting sheet 3 is topencilmark, the true north index T on plotting sheet 3 directly over thecircle 8 on grid disc 6. This is done by orienting one of the lines 9'parallel to one of the meridian lines found on all navigational maps.true north and index T can be indicated by a pencil-marked arrow. Thenext step is to pencilmark themagnetic index M on plotting sheet 3. Thisis accomplished with the aid of the graduations on circle 8 to measureoff the angle of variation in accordance with data given on the map.With maps having non-parallel meridians or showing areas where themagnetic variation changes rapidly, these pencil-marked indices arechanged to conform to the directions of true north and magnetic northfor the particular area of the map with which the navigator isconcerned.

The radius of the compass rose circle 8 is one hundred on the radialgrid scales along line 9. Therefore, when any heading and air speedvector such as I-IO in Fig. 3 is plotted from the circle to the pivotcenter 0 the grid scale divisions will represent percentages of the airspeed. Further,

The diametric line 9 then points to a wind vector such as O-W and atrack and ground speed vector such as HW can be plotted and air speedand angle of drift areknown as well as by other methods well understoodin the art.

Then with the diametric line 8 oriented parallel to the desired courseCA as shown in Fig. 3 the track and ground speed vector H-W is plottedbackwards freehand from the wind point W by the aid of the parallellines 3' until it intersects the compass rose circle 8 at H. The groundspeed thus obtained is a'percentage of air speed and can be read bynoting the length of vector HW using for this purpose the. gridsquares,each one of which represents 10 per cent of air speed. By multiplyingthis percentage times the air speed which is known, the ground speed inmiles per hour can be obtained. The magnetic heading necessary to makegood the specified course CA can then-be determined by orienting thediametric line 9 under vector H0 with the arrows on the scalor line 8pointing in the direction H-Oand reading the direction at thepencil-marked magnetic index M.

Another problem, the determination of position by the intersection oftwo radio compass bearings is also shown in Fig. 3. Assume A representsthe map position of a radio station at the destination and the line CAis a radio compass bearing 250 magnetic obtained while the plane is atan unknown position in the vicinity of C.

The line CA is plotted by setting 250 at index M. This fixes theposition of the plane somewhere along line CA. The line CB similarlyplotted from a radio compass bearing taken on station B fixes theposition of the plane at point C, the intersection of the two lines A-Cand 13-0 The method of measuring distances as described above is basedon the use of a grid scale equal to the scale of miles on the map.Aviation maps are constructed on scales which are convenient multipliesor fractions of the scale of 1/ 1,000,000. Thus, it can be seen that ifit is desired to use maps of diflferent scales a grid'construction onthe scale of 1/ 1,000,000 can still be used to measure distances by theuse of a suitable factor.

If desired my invention may be arranged as illustrated in Fig. 4,wherein I have shown an endless strip map l5 mounted on rollers l6.These rollers 16 are adapted to be turned on shafts H by knobs, notshown, so as to bring the desired area of the map on the upper side.Over this strip map is mounted a plotting sheet 3 and grid disc 6 asdescribed in connection with Figs. 1 and 2. Underneath the upper part ofstrip map I5 lighting means such as a plurality of electric lights l8are mounted so as to cause a diffused light to be visible down throughthe plotting sheet 3, grid disc 6 and map l5. This arrangement rendersthe details of the map and the plottings on sheet 3 easily discernablein the semi-darkness desirable in the control room of an airplane beingnavigated p 75 transparent member I r aliases at night. Further, it is asimple matter to move\ while I have referred to plotting sheet 8 andgrid disc 8 as being made up of celluloid. it will be understood that :7other suitable transpari cut material ialls thin the scope oimy'invention. It will be further understood that while I have shownlines 9' and I0 forming a grid, lines it are not entirely necessarysince it is possible to rotate the grid disc 90 and use lines l tomeasure distances. 7 Figs. 5, 6 and 7, which show the component parts ofthe preferred form and two modifications oi my invention respectively,illustrate 'various means for orienting grid discs with respect to maps.Fig. 5 shows the 'preierred term in which true indexT. andmagneticindex' M are pencil-marked on plotting sheet I for use with thecountercl ckwise compass rose 8 on grid disc 8 to measure/angularorientations of grid lines a with respect to true and magnetic north onmany 2, as described above. g V

In the modification shown in Fig. 6 the compass rose It is located onthe map and the true and magnetic indices are placed on the grid disc.Compass rose It on map 20 is on a radius of one hundred miles to scaleand is an ordinary or clockwise compass rose in proper orientation withrespect to true north on the map. Map 2D is arranged so that when it issecured under plotting oheet 2| the compass rose II will be concentricwith pivot 22 of the grid disc 21. The dlametric scelor line 24 oi thegriddisc It coacting with the compass rose is will then serve as a trueindex for measuring angular orientations of grid lines 24' withrespectto true north on the map. Likewise, a magnetic index Ill penoil-markedon the grid disc beside true index 24 through an opening N in theplottingsheet 2i will serve to measure orientations of the grid lineswith respect to magnetic north on the map.

the scale of map '30 is located on; plotting sheet It concentric withgrid disc pivot 20.. Map 3B is arrangedso that when secured to plottingsheet 2d the direction oi true north on the maria will coincide with thedirection of ill-on the com pass rose ill. The scalor line it will thenserve as a true index. And. a magnetic, index 32 may so be pencil-markedon the grid disc through opening Min plotting sheet as in themodificatiori described above.

While I have described what I consider to be the preferred embodimentsof my invention, it will oi course, be understood that I do not wishtemplate by the appended claims to cover all such modifications as fallwithin the true spirit and scope of my invention.

tlclaimasnew anddesiretosecureby Letters Patent is: g

1. A map holderand plotting device comprising a'map support, atransparent plotting member, means for securing said member in fixedorientation and fixed position overpaid map "support, a mend sparentmember mounted for rotation between said transparent plotting member andsaid map support. said second to be limited thereto since many othermodifica- 'tions may be made in the structure, and I 0012- delineamthereon. I l .t.

said second transparent member in desired angul'ar orientation withrespect to said map support.

2. A map holder and plotting device comprising a map support, atransparent plotting member, means for securing said member in fixedoilentation and fixed position over said map support. a secondtransparent member mounted for rotation between said transparentplotting member and said. map support, said second transparent memberhaving a series of parallel lines delineated thereon, and a compass roseon one oi said transparent members 'conwntric with the axis oil rotationoi said second transparentmember.

d. A map holder and plotting device comprising a map support, atransparent plotting member, means for seeming said member in fixedorientation and fixed position over sai map support, a secondtransparent member mounted ior rotation between saidtransparent plottingmember and said map support, said second transparent member carrying acompass; rose,

and, having a series oi parallel lines delineated thereon. i

i: A" map holder and plotting device comprising a map support. asuperposed transparent plotting member, a transparent protraotor memherhaving a series of parallel lines delineated thereon and being mountedfor rotation between said superposed member and said map support, andmeans for securing said superposed member to said p support in fixedrelation with respect thereto.

5. A map holder and plotting device comprising a map support, atransparent plotting 'member mounted over said map support, interposedtransparent protractor member having a series oi parallel linesdelineated thereon and mounted for rotation between said transparentplotting member and said map support, "and means for securing saidtraent plotting member to said map support said means inelud- I ing:menus ilor tig' said map support in fixed relation with pect to saidtrent plotting member.

6. d. map holder and plotting device compris ing a member having a maprepresented thereon,

a transparent plotting member mounted over said first mentioned member,s. circular transparent protractor member. pivotullr mounted imderheathsaid transparentplotting member and over said first mentioned member,said circular trans parent protractor member being a r to protrudebeyond the edgeoi said first mentioned member and the superposedtransparent plotting member whereby sa d protractor member may bemanipulated manually to orient the same.

'7. A map holder and plotting device comprising a map support adapted tohave n map folded tatable transparent protractor member minted eachrofsaid first referred to transas therearound, a transt plotting membermounted on each side of said map support, a 1'0- between parent membersand said map sup,

meant adjacent to et least one edge of o en! 'said transparent plottingmembers, seem-ing having ajseries ofparailel' m corresponiyrlocatod onthe other of said transparent plotting rnembem and elastic meansextending between coirerponding securing means on said. members toeecurcsaid members to one another on opposite dries of said map support.

8. A map holder and plotting device comprise 15 ing a map supportadapted to have a map folded therearound, a transparent plotting membermounted on each side of said map support, a rotatable transparentprotractor member mounted between each of said transparent plottingmembers and said map support, a hook located at each corner of'each ofsaid transparent plotting members and flexible means securing togethercorresponding hooks. on opposite members, said flexible means beingso-arranged around the corners 01 said transparent plotting members asto position said map support and map with respect thereto.

9. A map holder and plotting device comprising a map support, atransparent plotting member mounted over said map support, a transparentprotractor member pivotally mounted between said transparent plottingmember and said map support, said transparent protractor member being ofsuch dimensions that the edge thereof protrudes beyond one edge of saidmap support. whereby said protractor member may be manipulated manuallyto orient the same.

10. A map holder and plotting device compris-.

ing a map support, a transparent plotting member mounted over said mapsupport, a transparent protractor member pivotally mounted between saidtransparent plotting member and said map,

support, said transparent protractor member being of such dimensionsthat the edge thereof protrudes beyond the edge of said transparentplotting member whereby said protractor member may be manipulatedmanually to orient the same.

11. A map holder and plotting device comprising a member having a maprepresented thereon, a transparent plotting member, means for securingsaid plotting member in fixed orientation and fixed position over saidfirst mentioned member, a second transparent member mounted for rotationbetween saidtransparent plotting member and said first mentioned member,said second transparent member having delineated thereon a series ofparallel lines and means for setting said second transparent member indesired angular orientation with respect to said first mentioned member.

12. A map holder and plotting device comprising a member having a maprepresented thereon, a transparent plotting member, means for securingsaid plotting member in fixed orientation and fixed position over saidfirst mentioned member, a second transparent member mounted for rotationbetween said transparent plotting member and said first mentionedmember, said second 'transparent member having delineated thereon adiametric line and a series 01' lines parallel thereto, a circle beingdelineated on one of said fixed position over said first nientionedmember, a

transparent grid member mounted for rotation between said transparentplotting member and said first mentioned member, one of said mem bershaving a compass rose thereon concentric with theaxis of rotation ofsaid transparent grid member. 1

' 14. A map holder and plotting device comprising a member having a maprepresented thereon,

a transparent plotting member, mounted over said first mentioned member,a transparent grid member mounted for rotation between said transparentplotting member and said first mentioned member, said transparentplotting member having a compass rose thereon concentric with the axisof rotation of said transparent grid member, said compass rose beingoriented to correspond to the orientation of said map.

16. A map holder and plotting device comprising a member having a maprepresented thereon, a transparent plotting member, means for securingsaid plotting member in fixed orientation and fixed position over saidfirst mentioned member, a transparent grid member mounted for rotationbetween said transparent plotting member and said first mentionedmember, said map having a compass rose thereon concentric with the axisof rotation of said transparent grid member.

1'7. A map holder and plotting device comprising a member having a maprepresented on either side thereof, a transparent plotting membermounted on each side or said first mentioned member, a rotatabletransparent protractor member mounted between each of said transparentplotting members and said first mentioned member, and means for securingsaid transparent plotting members in fixed orientation and fixedposition with respect to said first mentioned member including a hooklocated at corresponding corners or each of said transparent plottingmembers and flexible means securing said hooks together, said flexiblemeans being so arranged around the corners of said transparent plottingmembers as to position said first mentioned member with respect to saidtransparent plotting members.

PHILIP DALTON. e

